Unity and Diversity of Life

UNITY AND DIVERSITY OF LIFE

BIOLOGY is the study of living organisms and their interactions with the environment. Therefore, this semester’s topics will include animals, plants, microbes, and fungi, as well as ecology (how they interact with the environment). Biology is the study of living things. But what is life? What distinguishes living from non-living things?

7 Properties Associated with life: 1) Order 2) Reproduction 3) Growth and development 4) Energy processing 5) Response to the environment 6) Regulation 7) Evolutionary adaptation

Order • This close-up of a sunflower illustrates the highly ordered structure that typifies life. Living cells are the basis of this complex organization. Reproduction • Organisms reproduce their own kind. Here, an emperor penguin protects its baby. Growth and Development • Inherited information in the form of DNA controls the pattern of growth and development of all organisms, including this hatching crocodile. Energy processing • When this bear eats its catch, it will use the chemical energy stored in the fish to power its own activities and chemical reactions. Response to the environment • All organisms respond to environmental stimuli. This Venus flytrap closed its trap rapidly in response to the stimulus of a damselfly landing on it. Regulation • Many types of mechanisms regulate an organism’s internal environment, keeping it within limits that sustain life. Here is a typical lemur behavior with a regulatory function (sunbathing), which helps raise the animal’s body temperature on cold mornings. Evolutionary adaptation • The leaf-like appearance of this katydid camouflages it in its environment. Such adaptations evolve over many generations as individuals with traits best suited to their environment have greater reproductive success and pass their traits to offspring. Scope of Biology • Biology is an enormous scope, and can be studied in two ways: • The vertical dimension is studying biology based on size from largest (the biosphere) to smallest (non-living molecules). • The horizontal dimension is studying biology across the great diversity of species, learning about classification of organisms.

1 UNITY AND DIVERSITY OF LIFE

THE VERTICAL DIMENSION OF BIOLOGY

THE BIOSPHERE The biosphere consists of all the environments on Earth that are inhabited by life. It includes land and water such as oceans, lakes, and rivers; it also includes the atmosphere to an altitude of several kilometers.

ECOSYSTEMS An ecosystem consists of all living things in a particular area, along with all the nonliving components of the environment with which life interacts, such as soil, water, atmospheric gases, and light. Examples of an ecosystem are forests or coral reefs.

COMMUNITIES A community is all of the living organisms within a particular ecosystem. The community of a forest includes all species of trees, plants, animals, fungi, and bacteria that live there. The tree in your backyard is home to two cardinals, a colony of ants, a wasp's nest, four squirrels, and trillions of bacteria. Together, all of these organisms represent a community.

POPULATIONS A population consists of all the individuals of a species living within the bounds of a specified area. For example, a forest may include a population of sugar maple trees, and a population of American black bears. We can now refine our definition of a community as the set of populations that inhabit a particular area.

ORGANISMS An organism is an individual living thing. Each of the maple trees and other plants in a forest is an organism, and so is each forest animal such as a frog, squirrel, bear, and insect. The soil is also full of micro organisms such as bacteria.

ORGANS AND ORGAN SYSTEMS An organ is a body part consisting of two or more tissues. Examples of human organs are the brain, heart, and kidney. Examples of a tree’s organs are its leaves, stems, and roots. An organ system is a group of organs which cooperate in a specific function. For example, the human digestive system includes such organs as the tongue, stomach, and intestines.

TISSUES A tissue is a group of similar cells which perform the same function. Examples of human tissues include the epidermis (skin), muscle, and bones. Leaves have one type of tissue on their surface which contains pores to allow carbon dioxide to reach the interior of the leaf. They have another type of tissue within the leaf, which is the area where of photosynthesis occurs.

CELLS The cell is the fundamental unit of structure and function of each organism. Some organisms, such as amoebas and most bacteria are single cells. Other organisms, including plants and animals, are multicellular. Instead of a single cell performing all the functions of life, the multicellular organism has a division of labor among specialized cells. In humans, examples of a specialized cell include a nerve cell (neuron), a muscle cell (myofibril), and a bone cell (osteocyte).

ORGANELLES An organelle is like a miniature organ within a single cell. It has a specific function for that cell. An example of an organelle in a human cell is a nucleus. An example of an organelle in a plant cell is a chloroplast.

MOLECULES A molecule is a chemical structure consisting of two or more atoms. If one of the atoms is carbon, it is an organic molecule. If there is no carbon, it is an inorganic molecule. An example of a plant molecule is chlorophyll. Examples of organic molecules used by animals are carbohydrates, proteins, and fats. Examples of inorganic molecules used by animals are salt and water.

Life is organized in a hierarchical fashion. The following sequence illustrates that hierarchy increases in complexity: Molecule, organelle, cell, tissue, organ, organ system, organism, population, community, ecosystem, and biosphere.

COURSE OVERVIEW

Within the vertical dimension of biology, one of the topics that we will spend considerable time on this semester is ecology, including ecosystem dynamics and energy conservation.

ECOSYSTEM DYNAMICS On the cover of your biology textbook is a pelican. They belong to a group of animals called Aves, also known as birds, which are believed to have evolved from ancient feathered dinosaurs. Pelicans have fishing skills that are well suited to the ocean habitat. They can dive into the ocean and catch a fish six the below the surface. There are hunting helps regulate the size of fish populations. Because it is comfortable floating on the waves, it is also an ideal scavenger. Small fishing boats can therefore toss away unwanted fish parts without polluting the water. But some fishermen see the birds as competition rather than trash collectors, and a slaughter thousands of the birds. Additionally, when humans use pesticides, the rain washes the pesticides into the soil, which gets carried into the water table, which leads to the oceans, where it accumulates in fish and birds that ate them. The pesticides will cause a bird to lay a very thin egg shell so that it breaks before it hatches. Because of this, a pelican population was almost wiped out. The birds first disappeared entirely from Louisiana and been banished from

3 UNITY AND DIVERSITY OF LIFE other coastal areas as well. In 1970 the brown pelican was declared an endangered species. Biologists argued that only a ban on pesticides such as DDT would save the birds, and in 1972 that ban was enacted. Because of these efforts, they are once again thriving in many coastal areas. However, as their numbers grow, they are continuing to face problems when they encounter humans. The young pelican on the cover of this book is at a bird sanctuary in Florida which cares for birds injured by boat propellers or fishing lines. All organisms are connected to the environment and other organisms.

Each organism interacts continuously with its environment, which includes other organisms as well as nonliving factors. For example, the roots of a tree absorb water and minerals from the soil. The leaves take in carbon dioxide from the air. Solar energy absorbed by chlorophyll drives photosynthesis, which converts water and carbon dioxide to sugar and oxygen. The tree releases oxygen to the air, and its roots help form soil by breaking up rocks. Both the organism and the environment are affected by the interactions between them. The tree also interacts with other of life, including soil microorganisms and animals that eat its leaves and fruit.

The dynamics of any ecosystem include two major processes. One process is the cycling of nutrients. For example, minerals acquired by plants will eventually be returned to the soil by microorganisms that decompose dead leaves, roots, and fruit. The second major process and an ecosystem is the flow of energy from sunlight  producers  consumers. Producers are plants and other photosynthetic organisms that convert light energy to chemical energy. Consumers are organisms, such as animals, that feed on producers and other consumers.

ENERGY CONSERVATION Moving, growing, reproducing, and other activities of life require organisms to perform work. Work depends on a source of energy. The exchange of energy between an organism and its surroundings often involves the transformation of one form of energy to another. For example, when a leaf produces sugar, it converts solar energy to chemical energy in the form of sugar molecules. When an animal’s muscle cells use sugar as fuel to power movements, they convert chemical energy in the form of sugar to kinetic energy (the energy of motion). During the course of these conversions of one energy form to another, thermal energy is dissipated to the environment in the form of heat. In contrast to chemical nutrients, which recycle within an ecosystem, energy flows through an ecosystem, usually entering the system as light and exiting the system as heat. The ultimate source of energy flowing into nearly all ecosystems is sunlight. The ultimate source of energy flowing out of nearly all ecosystems is heat.

CELLS’ HEREDITARY INFORMATION Another topic we will cover this semester is the structure and function of cells, including their role in nutrition, the function of enzymes and proteins, the use of energy, and how a cell reproduces.

A cell is the lowest level of organization that can perform all activities required for life. For example, the ability of a cell to divide and form new cells is the basis for all

4 UNITY AND DIVERSITY OF LIFE reproduction and for the growth and repair of multicellular organisms. Your every movement is based on the activities of your muscle cells. Your every thought is based on the activities of your nerve cells. Even the process of breathing is the cumulative product of cellular activities.

Within the nucleus of a cell there are structures called chromosomes, which are made out of DNA. On the chromosomes are genes, which are the units of inheritance that transmit information from parents to offspring. Your hair color, for example, is the result of genes that you inherited on your parents.

Each chromosome is a very long DNA molecule with hundreds or thousands of genes arranged along its length. The DNA of chromosomes replicates as a cell prepares to divide; therefore, each of the two offspring cells inherit a complete set of genes. Each of us began life as a single cell stocked with DNA inherited from our parents. Within the genes are molecules that encode the information for building the entire body. In this way, DNA directs development and maintenance of the entire organism.

Each DNA molecule is like a chain with many links. Each link of the chain is one of four kinds of chemical building blocks called nucleotides. The way DNA encodes a cell’s information is similar to the way we arrange letters of the alphabet into precise sequences with specific meanings. The word rat, for example, conjures up an image of a rodent. The words tar and art, which contained the same letters, mean very different things. Libraries are filled with books containing information encoded in varying sequences of only 26 letters. Our genetic information is likewise made out of only four nucleotides (letters of the alphabet); however each gene (word) may be thousands of letters in length.

Most genes program the cell’s production of large molecules called proteins. Each gene codes for a different protein which has a unique shape and function in the cell. One protein might be part of a muscle, while another protein might be an antibody. The DNA provides the hereditary blueprint for these proteins, but the proteins themselves are the tools that actually build and maintain the cell.

THE HORIZONTAL DIMENSION OF BIOLOGY

TAXONOMY Taxonomy is that part of biology dedicated to naming, describing, and classifying species. The categories are ordered into a series of groups of increasing breadths.

Until the last decade, taxonomy was divided into five kingdoms, including the plant and animal kingdoms. But with new understanding of DNA sequences, biologists are re- evaluating the system of classification. The debate over the number of kingdoms is still continuing, but there is a consensus that the kingdoms of life can now be grouped into three even higher levels of classification called domains. The three domains are named Bacteria, Archaea, and Eukarya.

Bacteria and Archaea are both prokaryotes (unicellular and microscopic). Eukaryotes are multicellular organisms, and include the kingdoms of plants, animals, and fungi.

Who are we? For humans, here is our classification: Domain: Eukarya Kingdom: Animal Phylum: Chordata Class: Mammalia Order: Primates Family: Hominidae Genus: Homo Species: sapiens (Memory Aid: Dashing King Phillip Came Over From Greece, Singing)

Animals What’s the difference between an animal and a plant? An animal can move from one place to another, they don’t get food from sunlight, and their body structure is fixed.

Mammals Mammals are born with a placenta and produce milk for the offspring.

Primates Primates have an opposable thumb (can touch each of the other fingers). Good depth perception because the eyes are in front of the head. Gestation (length of pregnancy) is lengthy. One birth at a time is the norm. Juvenile period of dependency is long. There is an emphasis on learned behavior and complex social interactions.

Humans and apes are both primates. There are four types of modern apes: gibbons, orangutans, gorillas, and chimpanzees. Humans can be distinguished from modern apes by walking upright, dental features, shape of face, and brain size.

Hominids • Make use of symbolic language (writing) • Walk on two legs Evolutionists say that our ancestors are Australopithecus, which evolved in eastern Africa 4 MYA (million years ago). The most famous Australopithecus fossil is called Lucy (The name derives from the Beatles’ song “Lucy in the Sky with Diamonds.”). Although her brain was quite small, Lucy walked upright. p Homo sapiens There is only one genus and species of hominids and that is Homo sapiens. In Latin, Homo sapiens means “wise or rational man”.

We Are One Species Bacteria, Archaea, plants, animals, and fungi are very diverse organisms. Even within our own species there are variation is race. Races are actually just slight differences in ethnicity that developed as an adaptation to the climate of a region. But inside plants, animals, fungi, and people, our molecules are all the same. Thus, there is unity within the diversity of life.

Match the following to their descriptions Animals-B A. walk on two legs, make use of symbolic language (writing) Mammals -C B. can move from one place to another, body structure is fixed. Primates -E C. born with a placenta and produce milk for the offspring. Hominids-A D. wise or rational man. Homo Sapiens -D E. Opposable thumb, long gestation, learned behavior

Match the following taxonomy terms for a human being Kingdom: C A. Homo Order: B B. Primate Family: E C. Animal Genus: A D. sapiens Species: D E. Hominid

EVOLUTION AND NATURAL SELECTION Also during the course of this semester, we will discuss the topic of evolution and natural selection.

• The history of life is documented by fossils and other evidence that the Earth and its life forms is changing and evolving. • This evolutionary view of life came into sharp focus in 1859, when Charles Darwin published one of the most controversial books ever written: The Origin of Species by Natural Selection. • This book articulated two main points. First, Darwin presented evidence to support his view that modern species arose from a succession of ancestors. • Darwin called this “descent with modification”. • This phrase captures both the unity of life (descent from common ancestors) and the diversity of life (modifications that evolved as species branched from their common ancestors).

Descent with Modification (Evolution) • Descent with modification implies that modern species arise from a common ancestor. • As evidence for this theory, the arms of a bat, human, horse’s forelegs, and whale flippers all contain the same skeletal architecture, including the same bones, joints, nerves, and blood vessels. • In the Darwinian view, the unity of mammalian limb anatomy indicates the inheritance of that structure from a common ancestor, the diversity of the

forelimbs having been modified by natural selection operating over millions of generations in different environmental conditions.

NATURAL SELECTION • Darwin's second main point was to propose a mechanism for evolution, which he called “natural selection”. • He started with two observations. 1) Individuals in a population vary in their traits, many of which are passed on from parents to offspring. 2) A population can produce far more offspring than the environment can support. • From these two observations, Darwin inferred that those individuals with heritable traits best suited to the environment are more likely to survive and reproduce than others. • As a result of this unequal reproductive success over many generations, a higher and higher proportion of individuals will have the best traits for survival. • The result of natural selection is evolutionary adaptation, the accumulation of favorable traits in a population over time.

Natural selection is when the natural environment selects for the propagation of certain traits. For instance, consider an area where the soil has been blackened by a recent brush fire. A population of insects there contains beetles that are either white or gray; a predator bird can easily pick out the white colored insects and the beetles with the white coloration are eliminated from the population. The survivors reproduce, carrying on their genetic coloration, enhancing the survival and reproductive success of the dark-colored bugs. This is natural selection.

SCIENTIFIC METHOD We will also spend some time on the scientific method so you understand what process a researcher goes through to document new discoveries.

The word “science” is derived from a Latin verb meaning “to know”. At the heart of science is inquiry, a search for information and explanation, often focusing on specific questions. Biology blends two main processes of scientific inquiry: discovery science and hypothesis-based science. Discovery science is mostly about describing nature. Hypothesis-based science is mostly about explaining nature. Most scientific inquiries combine these two research approaches.

Discovery science describes natural structures and process through careful observation and analysis of data. For example, discovery science gradually built our understanding of cell structure, and it is currently expanding our understanding of genetics. Observation is the use of senses to gather information, sometimes with the help of tools such as microscopes that extend our stances. Recorded observations are called data. Some data is qualitative, taking the form of recorded descriptions rather than measurements in numbers. For example, Jane Goodall spent decades recording her observations of

8 UNITY AND DIVERSITY OF LIFE chimpanzee behavior in the jungle. She also documented her observations with photographs and movies. In addition, she recorded behavior with quantitative data, recorded as specific measurements.

Hypothesis-based science starts with an observation that leads to a question about the cause or explanation for the observation. A hypothesis is a tentative answer to some question. It is usually an educated guess based on past experience and current knowledge. You notice that over the past month, many students have started wearing a new style of school sweatshirt. You think to yourself, maybe the bookstore recently started selling this new sweatshirt style. This prediction is an example of a hypothesis.

A scientific hypothesis makes a prediction that can be tested by designing an experiment. We all use hypotheses in solving everyday problems. For instance, suppose your flashlight stops working. That's an observation. The question is: Why doesn't the flashlight work? Two reasonable hypotheses are: 1. The batteries are dead 2. The bulb is burned-out Each of these alternative hypotheses makes predictions you can test with experiments. For example, the dead battery hypothesis predicts that replacing the batteries will fix the problem. The experiment is to replace the batteries with new ones. If the flashlight then works, the hypothesis was validated. In the flashlight does not work, the experiment falsifies the hypothesis. The second hypothesis can then be tested by replacing the light bulb.

This example illustrates two important qualities of scientific hypotheses. First, a hypothesis must be testable; there must be some way to check out the validity of the idea. Second, a hypothesis must be falsifiable; there must be some experiment that could reveal it such an idea is actually not true. To be scientifically valid, a hypothesis must be testable and falsifiable.

Ideally, an experiment should contain a “control” component. This means that two experiments are conducted, one differing from the other by only a single variable. The role of a control in an experiment is to provide a basis of comparison to the experimental group. For example, a company that sells cereal wants to prove that it lowers cholesterol. They find 1000 volunteers to eat this cereal for three months and have their cholesterol measured before and after the experiment. A proper experimental design should include another 1000 volunteers who are as similar as possible to the experimental group (in age, ethnicity, health status, etc.) who do not eat that cereal.

Another component of an ideal experiment is that all possible variables are eliminated between the control group and the experimental group. For example, if the volunteers who eat this cereal are all in their mid-- 20s and exercise daily, and the volunteers in the control group are middle aged and do not exercise, there are two variables in this experiment that were not eliminated. Thus, the results of the experiment are not valid.

An Actual Case Study of Hypothesis-Based Science

New discoveries in science start with the observation: Many poisonous animals are brightly colored so that predators will recognize them as poisonous and stay away. But there are also mimics. These imposters look like poisonous species but are actually harmless. After an observation comes a question: What is the function of such mimicry? And then a hypothesis is formed: Such deception is an evolutionary adaptation that reduces the harmless animal’s risk of being eaten.

In 2001, biologists David and Karin Pfenning, along with William Harcombe, one of their students, designed an experiment to test the hypothesis that “mimics benefit because predators confuse them with the harmful species”. A poisonous snake called the eastern coral snake has colored rings of red, yellow, and black. Predators rarely attack these snakes. The predators do not learn this avoidance behavior by trial and error; a first encounter with a coral snake would usually be deadly. Therefore, natural selection has apparently increased the frequency of predators that inherit an instinctive ability to recognize the coloration of the coral snake. A non-poisonous snake called the scarlet king snake mimics the ring coloration of the coral snake. (Humans can remember the difference by this phrase: red and yellow kill a fellow, red and black venom lack). Both types of snakes live in North and South Carolina, but the king snake’s geographical range also extends into regions where no coral snakes are found. This makes it possible for researchers to test a key prediction of the mimicry hypothesis: Mimicry should help protect king snakes from predators, but only in regions where coral snakes also live. Avoiding snakes with warning coloration is an adaptation of predator populations that have evolved in areas where the poisonous coral snakes are present. The mimicry hypothesis predicts that predators adapted to the warning coloration of coral snakes will attack king snakes less frequently then will predators in areas where coral snakes are absent.

The researchers placed equal numbers of artificial brown snakes and artificial coral snakes in field sites throughout North and South Carolina, including the region where coral snakes are absent. After four weeks, they retrieved the fake snakes and recorded how many had been attacked by looking for a bite or claw marks. The most common predators were foxes, coyotes, and raccoons, but Black Bears also attacked some of the artificial snakes.

The data fit the key prediction of the mimicry hypothesis. Compared to the brown artificial snakes, the ringed snakes were attacked by predators less frequently only in field sites within the geographic range of the poisonous coral snakes.

This case study provides an example of a controlled experiment, one that is designed to compare an experimental group (the artificial king snakes) with a control group (the artificial brown snakes). Ideally, the experimental and control groups differ only in the one factor the experiment is designed to test-- in our example, the effect of the snake’s coloration on the behavior of predators. Without the control group, the researchers would not have been able to rule out the number of predators in a different test areas as the cause of the different numbers of attacks on the artificial king snakes. The clever

10 UNITY AND DIVERSITY OF LIFE experimental design left coloration as the only factor that could account for the low predation rate on the artificial king snakes placed within the range of coral snakes.

SCIENCE, TECHNOLOGY, AND SOCIETY This semester, we will also discuss genetic research in our society, and how biotechnology benefits humanity. We will also talk about population and pollution concerns on our planet, including global warming.

Endangered species, genetically modified crops, global warming, air and water pollution, the cloning of embryos, nutrition controversies, emerging diseases, medical advances-- is there ever a day that we don't see several of these issues featured in the news? Biology, the science of life, has an enormous impact on our everyday life.

The goal of science is to understand natural phenomena. In contrast, technology generally applies scientific knowledge for some specific purpose. Science and technology can benefit society. The discovery of the structure of DNA 50 years ago has led to the many technologies of DNA engineering that are being used today in the field of medicine, agriculture, and genetics. The direction that technology takes depends on the wants and needs of people and on the social environment of the times.

With advances in technology come difficult choices. For example, under what circumstances is it acceptable to use DNA technology to check if people have genes for hereditary diseases? Should such tests always be voluntary, or are there any circumstances when genetic testing should be mandatory? Should insurance companies or employers have access to the information?

Technology has improved our standard of living in many ways, but not without consequences. Technology that keeps people healthier has enabled the earth's population to double to over 6 billion in just the past 40 years. The environmental effects of this growth can be devastating. Global warming, toxic wastes, acid rain, deforestation, nuclear accidents, and extinction of species are just some of the repercussions. Science can help us identify such problems and provide insight into what course of action may prevent further damage. But solutions to these problems have as much to do with politics, economics, and cultural values as with science and technology. Therefore, every citizen has a responsibility to develop a reasonable amount of scientific literacy.

Whether you are a scientist or not, issues come up at the poll booth for a vote and all citizens should be educated about how science works and about the potential benefits and risks of specific technology.

From the molecules to the biosphere, biology is directly connected to our everyday lives. This course will give you an education about the science of life and help you apply that understanding to evaluate issues ranging from your own personal health to the well-being of the whole world.